|Publication number||US7192800 B2|
|Application number||US 10/952,757|
|Publication date||Mar 20, 2007|
|Filing date||Sep 30, 2004|
|Priority date||Oct 8, 2003|
|Also published as||US20050079648|
|Publication number||10952757, 952757, US 7192800 B2, US 7192800B2, US-B2-7192800, US7192800 B2, US7192800B2|
|Original Assignee||Jidong Hou|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (7), Classifications (7), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This Application claims a priority date of Oct. 8, 2003 benefited from a previously filed Provisional Patent Application 60/509,234 filed on Oct. 8, 2003 by the Applicants of this Formal Patent Application.
Released membranes are usually used as moving parts in MEMS. The membranes are formed on sacrificial layers. When the sacrificial layers are etched away, membranes are released. The released membranes can move by deflection, and they often act as functional parts in MEMS (micro electro mechanic system). For example, they can have high reflectivity, acting as mirrors. In some applications of MEMS, such as optical filter, released membranes need some kinds of profiles, such as convex or concave surfaces, instead flat ones to perform well. The deflection by outside force will change the profile of released membranes, but the curvatures vary with deflection and usually the curvatures radii are very large. Compressive stress can be introduced on the membranes, leading a bow profile of membranes. Compressive stress will make membranes not easy to be released and the curvatures will vary with deflection. This method can not make surfaces with small curvature radii.
U.S. Pat. No. 6,768,756 gives a method to make curved membranes. In that patent, patterned photo resist is reflowed to make curved surface and this curved surface is transferred to a device layer by etching and membranes having optical properties are coated on the device layer. The device layer must be thick enough for forming curved surfaces. The membrane is attached to the device layer. Therefore, very large driving force is needed to move membranes. And some more optical membranes will be needed to eliminate the effect of the device layers if light pass through them.
The present invention discloses a method to change the profiles of released membranes. Curved surface on released membrane can be made by this method. This method introduces island structures on released membranes. Before being released, the island structures are top-hat regions of membranes. The materials of the island structures can be the same as the other part of the membrane or different from that. The membranes comprise one layer or several layers of different materials. At least one layer has intrinsic or residual stress. Because of the island structures, local strain can be introduced, and the surface of the island structures will change from being flat. The shape of the island structures can be round, square or any arbitrary one. This method has following advantages compared with previous ones: 1) The whole stress of membrane can still be tensile. Therefore, the releasing of membranes is easier than that having compressive stresses. 2) The curvature radii of the membranes at island region can be very small by adjusting the geometric parameters or material properties of the island structures. 3) The curvature of island region will not change or change very little when the whole parts of membranes deflect. 4) Since it is not attached to a thick device layer, the membrane is sensitive to diving force. If electrostatic forces are adopted, the corresponding driving voltages can be decreased.
The accompany drawings are not necessarily in scale, they just be used to illustrate the principles of this invention.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US7053737 *||Sep 19, 2002||May 30, 2006||Hrl Laboratories, Llc||Stress bimorph MEMS switches and methods of making same|
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|US20030031221 *||Sep 26, 2002||Feb 13, 2003||Coretek, Inc.||Single mode operation of microelectromechanically tunable, half-symmetric, vertical cavity surface emitting lasers|
|US20040066258 *||Jun 27, 2003||Apr 8, 2004||Cohn Michael B.||MEMS device with integral packaging|
|US20040252936 *||Jun 7, 2002||Dec 16, 2004||Michel Despont||Microsystem switches|
|US20050130360 *||Jan 5, 2005||Jun 16, 2005||Sharp Laboratories Of America, Inc.||Piezo-TFT cantilever MEMS|
|US20050226281 *||Mar 10, 2003||Oct 13, 2005||Lorenzo Faraone||Tunable cavity resonator and method of fabricating same|
|International Classification||H01L21/00, B81B3/00, H01L21/302|
|Cooperative Classification||B81C2201/0167, B81B3/0072|
|Aug 9, 2010||FPAY||Fee payment|
Year of fee payment: 4
|Oct 31, 2014||REMI||Maintenance fee reminder mailed|
|Mar 20, 2015||LAPS||Lapse for failure to pay maintenance fees|
|May 12, 2015||FP||Expired due to failure to pay maintenance fee|
Effective date: 20150320